Ethical, clinical, and economic considerations highlight the pressing need to advance the identification of optimal treatments for each individual patient. Personalized health care (PHC) may provide a significant benefit in the treatment of a number of clinical indications characterized by costly therapy, low response rates, and significant problems associated with trial and error prescription, including the risk of serious side effects. As an example, we focused on the promise of PHC for the field of rheumatology, in particular the use of diagnostic practice in guiding the treatment of rheumatoid arthritis (RA).